Sheet feeding apparatus

ABSTRACT

A sheet feeding apparatus includes a sheet feeding channel, a sheet feeding structure, a sheet stopping structure, plural sensing arms, an optical sensor and a controller. By the sheet feeding structure, a paper sheet is fed into the sheet feeding channel. The sheet stopping structure is used for stopping the paper sheet from being moved forwardly. During the process of feeding the paper sheet, the plural sensing arms are pushed by the paper sheet to be rotated. According to the rotating statuses of the sensing arms, the optical sensor issues different signals to the controller. According to these signals, the controller will control the operations of the sheet stopping structure and the sheet feeding structure, thereby correcting the skew condition.

FIELD OF THE INVENTION

The present invention relates to a sheet feeding apparatus, and more particularly to a sheet feeding apparatus having a mechanism for correcting the skew condition of feeding a document.

BACKGROUND OF THE INVENTION

Nowadays, a sheet feeding apparatus is widely applied to an office machine such as a printer, a copier, a deposit machine, or the like. The object of the sheet feeding apparatus is to feed a document into the office machine for performing the subsequent printing task. However, if a skew condition occurs during the process of feeding a document, the document will be aslant fed into the office machine, and thus the data fail to be printed on the actual positions of the document by the print head of the office machine.

For solving the above drawbacks, a sheet feeding apparatus with a mechanism for correcting the skew condition of feeding a document has been disclosed. FIG. 1 is a schematic side view illustrating a sheet feeding apparatus according to the prior art. FIG. 2 is a schematic perspective view illustrating a portion of the sheet feeding apparatus of FIG. 1. Please refer to FIGS. 1 and 2. The sheet feeding apparatus 1 comprises an upper casing 11, a lower casing 12, a sheet feeding channel 13, two feed rollers 14, two feed roller shafts 15, plural sheet stopping arms 16, a sheet stopping shaft 17, a controller 18 and plural optical sensors 19.

The sheet feeding channel 13 is arranged between the upper casing 11 and the lower casing 12 to be served as a transmission channel of the paper sheet P1. The feed roller shafts 15 are disposed within the upper casing 11 and the lower casing 12, respectively. The both ends of one of the feed roller shafts 15 are penetrated through two sides of the upper casing 11, respectively. The both ends of the other feed roller shafts 15 are penetrated through two sides of the lower casing 12, respectively. The feed rollers 14 are fixedly connected with respective feed roller shafts 15. Upon rotation of the feed roller shafts 15, the feed rollers 14 are synchronously rotated, so that the paper sheet P1 within the sheet feeding channel 13 is fed forwardly in the direction D1. Moreover, the sheet stopping shaft 17 is disposed within the lower casing 12 and in parallel with the feed roller shaft 15. The both ends of the sheet stopping shaft 17 are also penetrated through the two sides of the lower casing 12, respectively. The sheet stopping arms 16 are disposed on the sheet stopping shaft 17 and arranged along a direction D2 for stopping the paper sheet P1 from being advanced in the direction D1, wherein the direction D2 is perpendicular to the direction D1.

Each of the optical sensors 19 comprises a light transmitter 191 and a light receiver 192. The light transmitters 191 of these optical sensors 19 are disposed on the bottom surface of the lower casing 12 and extended along the direction D2. Corresponding to the locations of the light transmitters 191, the light receivers 192 of these optical sensors 19 are disposed on the top surface of the upper casing 11. The bottom surface of the upper casing 11 and the top surface of the lower casing 12 have plural openings 10, which are aligned with the light receivers 192 and the light transmitters 191. When one of the light transmitters 191 emits light beam, the light beam is transmitted through the corresponding opening 10 to be received by the corresponding light receiver 192. Moreover, in a case that the light beam from the light transmitter 191 is received by the corresponding light receiver 192 of the optical sensor 19, the optical sensor 19 generates a first signal. Whereas, in case that the light beam from the light transmitter 191 is not received by the corresponding light receiver 192 of the optical sensor 19, the optical sensor 19 generates a second signal.

Moreover, the controller 18 is electrically connected with the optical sensors 19 and the sheet stopping shaft 17. According to the signals outputted from the optical sensors 19, the controller 18 may control the operations of the sheet stopping shaft 17.

Please refer to FIGS. 3A-3D, which schematically illustrate the process of feeding the paper sheet into the sheet feeding channel in a skew condition. When the paper sheet P1 is aslant fed, a first side of the front edge is firstly sustained against the sheet stopping arms 16 (see FIG. 3A). At the same time, since some of the light transmitters 191 of the optical sensors 19 are sheltered by the paper sheet P1, the light beam from the light transmitters 191 fails to be received by corresponding light receivers 192. Under this circumstance, the corresponding optical sensors 19 generate second signals to the controller 18, but the other optical sensors 19 generates first signals to the controller 18. Next, since the feed roller shafts 15 are continuously rotated to feed the paper sheet P1, the portion of the front edge of the paper sheet P1 that is originally separated from the sheet stopping arms 16 will be gradually moved toward the sheet stopping arms 16. In other words, the number of the light transmitters 191 of the optical sensors 19 that are sheltered by the paper sheet P1 is gradually increased until the optical sensors 19 within the width range of the paper sheet P1 are all sheltered (see FIGS. 3B and 3C). Under this circumstance, the corresponding optical sensors 19 within the width range of the paper sheet P1 generate the second signals to the controller 18. After the second signals outputted from all optical sensors 19 are received by the controller 18, the controller 18 will control the sheet stopping shaft 17 to rotate in the direction D3. As the sheet stopping shaft 17 is rotated in the direction D3, the sheet stopping arms 16 are toppled down. Under this circumstance, the paper sheet P1 can be fed forwardly without being stopped by the sheet stopping arms 16 (see FIG. 3D). After the above actions have been done, the skew condition of the paper sheet P1 outputted from the sheet feeding apparatus 1 has been corrected.

However, since the conventional sheet feeding apparatus has too many optical sensors, the fabricating cost of the sheet feeding apparatus is very high. In other words, the sheet feeding apparatus is not cost-effective.

Therefore, there is a need of providing an improved sheet feeding apparatus to obviate the drawbacks encountered from the prior art.

SUMMARY OF THE INVENTION

The present invention provides a sheet feeding apparatus, which is cost-effective and capable of correcting the skew condition of feeding a document.

In accordance with an aspect of the present invention, there is provided a sheet feeding apparatus. The sheet feeding apparatus includes a sheet feeding channel, a sheet feeding structure, a sheet stopping structure, plural sensing arms, at least one optical sensor and a controller. The sheet feeding structure is used for allowing at least one paper sheet within the sheet feeding channel to be fed forwardly in a first direction. The sheet stopping structure is used for stopping the at least one paper sheet from being moved in the first direction. The plural sensing arms are disposed between the sheet feeding structure and the sheet stopping structure and arranged along a second direction, which is perpendicular to the first direction. Each of the sensing arms includes a contacting terminal, a sheltering terminal and a rotary part. The rotary part is arranged between the contacting terminal and the sheltering terminal. When the at least one paper sheet is contacted with the contacting terminal, the sensing arm is rotated by using a center axel of the rotary part as a pivot. The at least one optical sensor includes a light transmitter and a light receiver. When a light beam from the light transmitter is received by the light receiver, the optical sensor issues a first signal. Whereas, when the light beam from the light transmitter is sheltered by the sheltering terminal of any sensing arm, the light beam fails to be received by the light receiver, and the optical sensor issues a second signal. The controller is connected with the optical sensor and the sheet stopping structure. If the first signal, the second signal and the first signal are sequentially received by the controller, the sheet stopping structure is controlled by the controller to allow the at least one paper sheet to be continuously moved forwardly in the first direction.

In an embodiment, the sheet feeding apparatus further includes a feed sensing module for detecting whether the at least one paper is placed in the sheet feeding channel. The controller is connected with the sheet feeding structure and the feed sensing module. When the feed sensing module detects that the at least one paper is placed in the sheet feeding channel, the feed sensing module issues a third signal to the controller. In response to the third signal, the sheet feeding structure is enabled by the controller.

In an embodiment, the feed sensing module includes a second optical sensor and a feed sensing structure. The second optical sensor includes a second light transmitter for emitting a second light beam and a second light receiver for receiving the second light beam. The feed sensing structure includes a sheet feeding part, a sensing part and a rotary shaft. The sheet feeding part and the sensing part are fixedly connected with the rotary shaft, and the sensing part is arranged between the second light transmitter and the light receiver. When the at least one paper sheet is not contacted with the sheet feeding part, the second light beam from the second light transmitter is sheltered by the sensing part, so that the second light beam from the second light transmitter fails to be received by the second light receiver. Whereas, when the at least one paper sheet is contacted with the sheet feeding part to push the sheet feeding part, the sheet feeding part is rotated by using the rotary shaft as a pivot and the sensing part is rotated with the sheet feeding part, so that the second light beam from the second light transmitter is received by the second light receiver.

In an embodiment, the feed sensing module includes a second optical sensor and a feed sensing structure. The second optical sensor includes a second light transmitter for emitting a second light beam and a second light receiver for receiving the second light beam. The feed sensing structure includes a sheet feeding part, a sensing part and a rotary shaft. The sheet feeding part and the sensing part are fixedly connected with the rotary shaft. When the at least one paper sheet is not contacted with the sheet feeding part, the second light beam from the second light transmitter is received by the second light receiver. Whereas, when the at least one paper sheet is contacted with the sheet feeding part to push the sheet feeding part, the sheet feeding part is rotated by using the rotary shaft as a pivot and the sensing part is rotated with the sheet feeding part, so that the second light beam from the second light transmitter is sheltered by the sensing part and fails to be received by the second light transmitter.

In an embodiment, the sheet feeding structure includes a feed roller and a feed roller shaft. The feed roller is fixedly connected with the feed roller shaft, and the feed roller is rotated as the feed roller shaft is rotated.

In an embodiment, the sheet stopping structure includes plural sheet stopping arms and a sheet stopping shaft. The sheet stopping shaft is parallel with the feed roller shaft. The plural sheet stopping arms are disposed on the sheet stopping shaft and arranged along the second direction.

In an embodiment, the sheet feeding apparatus further includes a fixing shaft, wherein both ends of the fixing shaft are respectively fixed on two sides of the sheet feeding apparatus, and the rotary part of each sensing arm is pivotally coupled with the fixing shaft.

In an embodiment, the rotary part of each sensing arm is a cylindrical post.

The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view illustrating a sheet feeding apparatus according to the prior art;

FIG. 2 is a schematic perspective view illustrating a portion of the sheet feeding apparatus of FIG. 1;

FIG. 3A schematically illustrates a first stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 1 in a skew condition;

FIG. 3B schematically illustrates a second stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 1 in a skew condition;

FIG. 3C schematically illustrates a third stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 1 in a skew condition;

FIG. 3D schematically illustrates a fourth stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 1 in a skew condition;

FIG. 4 is a schematic side view illustrating a sheet feeding apparatus according to an embodiment of the present invention;

FIG. 5 is a schematic perspective view illustrating a portion of the sheet feeding apparatus of FIG. 4;

FIG. 6 is a schematic exploded view illustrating a portion of the sheet feeding apparatus of FIG. 4;

FIG. 7A schematically illustrates a sensing arm of the sheet feeding apparatus of FIG. 4 in a non-sheltered position;

FIG. 7B schematically illustrates a sensing arm of the sheet feeding apparatus of FIG. 4 in a sheltered position;

FIG. 7C schematically illustrates a sensing arm of the sheet feeding apparatus of FIG. 4 in another non-sheltered position;

FIG. 8A schematically illustrates a first stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a non-skew condition;

FIG. 3B schematically illustrates a second stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a non-skew condition;

FIG. 8C schematically illustrates a third stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a non-skew condition;

FIG. 8D schematically illustrates a fourth stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a non-skew condition;

FIG. 9A schematically illustrates a first stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a skew condition;

FIG. 9B schematically illustrates a second stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a skew condition;

FIG. 9C schematically illustrates a third stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a skew condition;

FIG. 9D schematically illustrates a fourth stage of a process of feeding the paper sheet into the sheet feeding channel of the sheet feeding apparatus of FIG. 4 in a skew condition;

FIG. 10A schematically illustrates a first stage of the actions of plural sensing arms and the optical sensor of feeding the paper sheet by the sheet feeding apparatus of FIG. 4 in a skew condition;

FIG. 10B schematically illustrates a second stage of the actions of plural sensing arms and the optical sensor of feeding the paper sheet by the sheet feeding apparatus of FIG. 4 in a skew condition;

FIG. 10C schematically illustrates a third stage of the actions of plural sensing arms and the optical sensor of feeding the paper sheet by the sheet feeding apparatus of FIG. 4 in a skew condition;

FIG. 11 is a schematic perspective view illustrating a portion of a sheet feeding apparatus according to another embodiment of the present invention; and

FIG. 12 is a schematic perspective view illustrating another exemplary feed sensing module used in the sheet feeding apparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 4 is a schematic side view illustrating a sheet feeding apparatus according to an embodiment of the present invention. FIG. 5 is a schematic perspective view illustrating a portion of the sheet feeding apparatus of FIG. 4. FIG. 6 is a schematic exploded view illustrating a portion of the sheet feeding apparatus of FIG. 4. Please refer to FIGS. 4, 5 and 6. The sheet feeding apparatus 2 comprises an upper casing 21, a lower casing 22, a sheet feeding channel 23, a sheet feeding structure 24, a sheet stopping structure 25, an optical sensor 26, a controller 27, a fixing shaft 28 and plural sensing arms 29.

The sheet feeding channel 23 is arranged between the upper casing 21 and the lower casing 22 to be served as a transmission channel of the paper sheet P2. This embodiment is illustrated by referring to a single paper sheet. Nevertheless, the sheet feeding apparatus 2 may be used to feed plural paper sheets which are bound together (e.g. a deposit book). By the sheet feeding structure 24, the paper sheet P2 within the sheet feeding channel 23 is fed forwardly in a first direction D4. In this embodiment, the sheet feeding structure 24 comprises a first feed roller shaft 241, a second feed roller shaft 242, a first feed roller 243 and a second feed roller 244. The first feed roller shaft 241 is disposed within the upper casing 21. The both ends of the first feed roller shaft 241 are penetrated through two sides of the upper casing 21, respectively. The second feed roller shaft 242 is disposed within the lower casing 22. The both ends of the second feed roller shaft 242 are penetrated through two sides of the lower casing 22, respectively. Moreover, the first feed roller 243 and the second feed roller 244 are respectively fixedly connected with the first feed roller shaft 241 and the second feed roller shaft 242 for feeding the paper sheet P2 forwardly in the direction D4. In a case that the first feed roller shaft 241 and the second feed roller shaft 242 are respectively rotated in the direction D5 and the direction D6, the paper sheet P2 between the first feed roller shaft 241 and the second feed roller shaft 242 will be fed forwardly in the first direction D4.

By the sheet stopping structure 25, the paper sheet P2 within the sheet feeding channel 23 is stopped from being moved forwardly in the first direction D4. In this embodiment, the sheet stopping structure 25 comprises a sheet stopping shaft 251 and plural sheet stopping arms 252. The sheet stopping shaft 251 is disposed within the lower casing 22 and parallel with the second feed roller shaft 242. The both ends of the sheet stopping shaft 251 are penetrated through the two sides of the lower casing 22, respectively. The sheet stopping arms 252 are disposed on the sheet stopping shaft 17 and arranged along a second direction D7, wherein the second direction D7 is perpendicular to the first direction D4. Moreover, as the sheet stopping shaft 251 is rotated, these sheet stopping arms 252 are synchronously rotated to with respect to the shaft center of the sheet stopping shaft 251.

Moreover, the optical sensor 26 is disposed within the lower casing 22. The optical sensor 26 comprises a light transmitter 261 and light receiver 262, which are arranged at bilateral sides of the optical sensor 26. The light transmitter 261 is used for emitting light beam. The light receiver 262 is used for receiving the light beam from the light transmitter 261. In a case that the light beam from the light transmitter 261 is received by the light receiver 262, the optical sensor 26 generates a first signal. Whereas, in case that the light beam from the light transmitter 261 is not received by the corresponding light receiver 262, the optical sensor 26 generates a second signal. Moreover, the controller 27 is electrically connected with the optical sensor 26 and the sheet stopping shaft 251. According to the signals outputted from the optical sensors 26, the controller 27 controls operations of the sheet stopping shaft 251.

The sensing arms 29 are disposed between the sheet feeding structure 24 and the sheet stopping structure 25, and arranged along the second direction D2. Each of the sensing arms 29 comprises a contacting terminal 291, a sheltering terminal 292 and a rotary part 293. The rotary part 293 is arranged between the contacting terminal 291 and the sheltering terminal 292. The rotary part 293 of each sensing arm 29 is a cylindrical post and pivotally coupled with the fixing shaft 28. The sheltering terminal 292 of each sensing arm 29 is arranged between the two sides of the optical sensor 26. The both ends of the fixing shaft 28 are penetrated through and fixed on the two sides of the lower casing 22, respectively. Consequently, in response to a pushing force, each of the sensing arms 29 is rotated by using the center axel of the rotary part 293 as a pivot. That is, the contacting terminal 291 and the sheltering terminal 292 are pivotal about the fixing shaft 28.

Hereinafter, the actions of the sensing arms of the sheet feeding apparatus 2 of the present invention will be illustrated with reference to FIGS. 7A, 7B and 7C. FIG. 7A schematically illustrates a sensing arm of the sheet feeding apparatus of FIG. 4 before the sensing arm is rotated. FIG. 7B schematically illustrates a sensing arm of the sheet feeding apparatus of FIG. 4 during the sensing arm is rotated. FIG. 7C schematically illustrates a sensing arm of the sheet feeding apparatus of FIG. 4 after the sensing arm is rotated.

In a case that all contacting terminals 291 of the sensing arms 29 are protruded through the openings 20 of the lower casing 22 and no pushing forces are exerted on the contacting terminals 291, all sheltering terminals 292 are not arranged between the light transmitter 261 and the light receiver 262 of the optical sensor 26. Under this circumstance, since the light beam from the light transmitter 261 can be received by the light receiver 262 of the optical sensor 26, the optical sensor 26 issues a first signal to the controller 27. When the contacting terminal 291 of any sensing arm 29 is pushed by the pushing force, the sensing arm 29 is rotated and thus the contacting terminal 291 is gradually toppled down toward the lower casing 22. Moreover, during the sensing arm 29 is rotated, the sheltering terminal 292 is rotated to a position between the light transmitter 261 and the light receiver 262 of the optical sensor 26, so that the light beam from the light transmitter 261 is sheltered by the sheltering terminal 292. Under this circumstance, since the light beam from the light transmitter 261 fails to be received by the light receiver 262 of the optical sensor 26, the optical sensor 26 issues a second signal to the controller 27. Until all contacting terminals 291 of the sensing arms 29 within the width range of the paper sheet P2 are toppled down to be sunk within the lower casing 22 in response to the corresponding pushing forces, these sheltering terminals 292 are no longer arranged between the light transmitter 261 and the light receiver 262 of the optical sensor 26. Under this circumstance, since the light beam from the light transmitter 261 can be received by the light receiver 262 of the optical sensor 26 again, the optical sensor 26 issues the first signal to the controller 27.

Hereinafter, a process of feeding the paper sheet P2 by the sheet feeding apparatus 2 of the present invention in a non-skew condition will be illustrated with reference to FIGS. 8A, 8B, 8C and 8D. FIGS. 8A, 8B, 8C and 8D schematically illustrate a process of feeding the paper sheet by the sheet feeding apparatus of FIG. 4 in a non-skew condition. After the paper sheet P2 is placed into the sheet feeding channel 23 of the sheet feeding apparatus 2, the paper sheet P2 is moved forwardly in the first direction D4 by the first feed roller shaft 241 and the second feed roller shaft 242. Under this circumstance, the front edge of the paper sheet P2 is still separated from the contacting terminal 291 of any sensing arm 29 (see FIG. 8A). Consequently, the optical sensor 26 issues the first signal to the controller 27.

Then, the first feed roller shaft 241 and the second feed roller shaft 242 are continuously rotated to feed the paper sheet P2 in the first direction D4. Since the paper sheet P2 is not aslant fed into the sheet feeding channel 23, all contacting terminals 291 of the sensing arms 29 within the width range of the paper sheet P2 will be simultaneously contacted with the front edge of the paper sheet P2. In response to the pushing forces provided by the front edge of the paper sheet P2, all contacting terminals 291 of the sensing arms 29 within the width range of the paper sheet P2 are rotated. Consequently, all contacting terminals 291 of the sensing arms 29 within the width range of the paper sheet P2 are gradually toppled down toward the lower casing 22. Until all contacting terminals 291 of the sensing arms 29 within the width range of the paper sheet P2 are toppled down to be sunk within the lower casing 22, the paper sheet P2 is allowed to be transported across the sensing arms 29 (see FIGS. 8B and 8C).

The actions of the sheltering terminals 292 will be illustrated as follow. Before the sensing arms 29 are rotated, all sheltering terminals 292 of the sensing arm 29 within the width range of the paper sheet P2 are not arranged between the light transmitter 261 and the light receiver 262 of the optical sensor 26. During the sensing arms 29 are rotated, all sheltering terminals 292 of the sensing arm 29 within the width range of the paper sheet P2 are rotated to the region between the light transmitter 261 and the light receiver 262 of the optical sensor 26, so that the light beam from the light transmitter 261 is sheltered by the sheltering terminals 292. After the sensing arms 29 are rotated, all sheltering terminals 292 of the sensing arm 29 within the width range of the paper sheet P2 are no longer arranged between the light transmitter 261 and the light receiver 262 of the optical sensor 26. As a consequence, the first signal, the second signal and the first signal from the optical sensor 26 are sequentially received by the controller 27. Afterwards, under control of the controller 27, the sheet stopping shaft 251 is rotated in the direction D8 to topple down all sheet stopping arms 252. Under this circumstance, the paper sheet P2 can be fed forwardly without being stopped by the sheet stopping arms 252 (see FIG. 8D).

Hereinafter, a process of feeding the paper sheet P2 by the sheet feeding apparatus 2 of the present invention in a skew condition will be illustrated with reference to FIGS. 9A-9D and FIGS. 10A-10C. FIGS. FIGS. 9A-9D schematically illustrate a process of feeding the paper sheet by the sheet feeding apparatus of FIG. 4 in a skew condition. FIGS. 10A-10C schematically illustrate the actions of plural sensing arms and the optical sensor of feeding the paper sheet by the sheet feeding apparatus of FIG. 4 in a skew condition. After the paper sheet P2 is placed into the sheet feeding channel 23 of the sheet feeding apparatus 2, the paper sheet P2 is moved forwardly in the first direction D4 by the first feed roller shaft 241 and the second feed roller shaft 242. Under this circumstance, the front edge of the paper sheet P2 is still separated from the contacting terminal 291 of any sensing arm 29 (see FIGS. 9A and 10A). Consequently, the optical sensor 26 issues the first signal to the controller 27.

Then, the first feed roller shaft 241 and the second feed roller shaft 242 are continuously rotated to feed the paper sheet P2 in the first direction D4. Since the paper sheet P2 is aslant fed into the sheet feeding channel 23, some of the contacting terminals 291 of the sensing arms 29 will be contacted with a first side of the front edge of the paper sheet P2. In response to the pushing forces provided by the front edge of the paper sheet P2, some of the contacting terminals 291 of the sensing arms 29 are rotated. Consequently, some of the contacting terminals 291 of the sensing arms 29 are gradually toppled down toward the lower casing 22. Until these contacting terminals 291 of the sensing arms 29 are toppled down to be sunk within the lower casing 22, the first side of the front edge of the paper sheet P2 is allowed to be transported across the sensing arms 29. Then, the first side of the front edge of the paper sheet P2 is stopped by the sheet stopping arms 252 from being moved forwardly. Then, since the first feed roller shaft 241 and the second feed roller shaft 242 are continuously rotated to feed the paper sheet P2, the portion of the front edge of the paper sheet P2 that is originally separated from the sheet stopping arms 252 will be gradually moved toward the sheet stopping arms 252. Consequently, these sensing arms 29 are gradually pushed by the paper sheet P2 to be rotated.

During the sensing arms 29 are rotated, the positions of all sheltering terminals 292 of the sensing arm 29 are different. In addition, the light beam from the light transmitter 261 of the optical sensor 26 is sequentially sheltered by the sheltering terminals 292 of different sensing arm 29 until all contacting terminals 291 of the sensing arms 29 within the width range of the paper sheet P2 are toppled down to be sunk within the lower casing 22. As a consequence, the first signal, the second signal and the first signal from the optical sensor 26 are sequentially received by the controller 27. Meanwhile, the skew condition of the paper sheet P2 within the sheet feeding channel 23 has been corrected. Afterwards, under control of the controller 27, the sheet stopping shaft 251 is rotated in the direction D8 to topple down all sheet stopping arms 252. Under this circumstance, the paper sheet P2 can be fed forwardly without being stopped by the sheet stopping arms 252 (see FIGS. 9C, 9D and 10C)

From the above description, since the skew condition of the paper sheet outputted from the sheet feeding apparatus of the present invention is effectively corrected, the printing task of the office machine applied to the sheet feeding apparatus can be actually done. Moreover, since not too many optical sensors are used, the sheet feeding apparatus of the present invention is more cost-effective.

FIG. 11 is a schematic perspective view illustrating a portion of a sheet feeding apparatus according to another embodiment of the present invention. Except that the sheet feeding apparatus 3 of this embodiment further comprises a feed sensing module 30 and the controller (not shown) is electrically connected with the sheet feeding structure 34 and the feed sensing module 30, the other components of the sheet feeding apparatus are similar to those of the sheet feeding apparatus 2 of the above embodiment, and are not redundantly described herein. When the feed sensing module 30 detects that the paper sheet P2 is placed in the sheet feeding channel 33, the feed sensing module 30 issues a third signal to the controller. In response to the third signal, the operations of the sheet feeding structure 34 are enabled by the controller. That is, before the paper sheet P2 is placed in the sheet feeding channel 33, even if the sheet feeding apparatus 3 is powered on, the operations of the sheet feeding structure 34 are stopped. In such way, a power-saving purpose is achieved.

The operating principles of the feed sensing module 30 will be illustrated in more details as follows. As shown in FIG. 11, the feed sensing module 30 comprises another optical sensor 301 and a feed sensing structure 302. The optical sensor 301 comprises a light transmitter 3011 and a light receiver 3012. The light transmitter 3011 is used for emitting light beam. The light receiver 3012 is used for receiving the light beam from the light transmitter 3011. The feed sensing structure 302 comprises a sheet feeding part 3021, a sensing part 3022 and a rotary shaft 3023. The sheet feeding part 3021 and the sensing part 3022 are fixedly connected with the rotary shaft 3023. The sheet feeding part 3021 is protruded upwardly through an opening 321 of the lower casing 32. The sensing part 3022 is arranged between the light transmitter 3011 and the light receiver 3012 of the optical sensor 301. In addition, the both ends of the rotary shaft 3023 are penetrated through the two sides of the lower casing 32. When the paper sheet P2 is not contacted with the sheet feeding part 3021, the light beam from the light transmitter 3011 is sheltered by the sensing part 3022, and thus the light beam fails to be received by the light receiver 3012. When the paper sheet P2 is placed in the sheet feeding channel 33 and contacted with the sheet feeding part 3021, the sheet feeding part 3021 is pushed by the paper sheet P2. Consequently, the sheet feeding part 3021 is rotated in the direction D9 by using the rotary shaft 3023 as a pivot until the sheet feeding part 3021 is completely toppled down to be sunk within the lower casing 32. Since the sensing part 3022 is also rotated with the sheet feeding part 3021 in the direction D9, the light beam from the light transmitter 3011 can be received by the sensing part 3022. Under this circumstance, the optical sensor 301 issues a third signal to the controller (not shown). In response to the third signal, the sheet feeding structure 34 is controlled by the controller to start feeding the paper sheet P2 forwardly in the first direction D4.

FIG. 12 is a schematic perspective view illustrating another exemplary feed sensing module used in the sheet feeding apparatus of the present invention. Except for the following mechanism, the configurations of the sheet feeding apparatus 4 are substantially identical to those of the sheet feeding apparatus in the above embodiment, and are not redundantly described herein. When the paper sheet P2 is not contacted with the sheet feeding part 4021, the light beam from the light transmitter 4011 of the optical sensor 401 of the feed sensing module 40 can be received by the sensing part 4022. When the paper sheet P2 is placed in the sheet feeding channel 43 and contacted with the sheet feeding part 4021, the sheet feeding part 4021 is pushed by the paper sheet P2. Consequently, the sheet feeding part 4021 is rotated in the direction D9 by using the rotary shaft 4023 as a pivot. Since the sensing part 4022 is also rotated with the sheet feeding part 4021 in the direction D9, the sensing part 4022 is toppled down. Meanwhile, the light beam from the light transmitter 4011 is sheltered by the sensing part 4022, and thus the light beam fails to be received by the light receiver 4012. Under this circumstance, the optical sensor 401 issues a third signal to the controller (not shown). In response to the third signal, the sheet feeding structure 34 is controlled by the controller to start feeding the paper sheet P2 forwardly in the first direction D4.

While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures. 

1. A sheet feeding apparatus, comprising: a sheet feeding channel; a sheet feeding structure for allowing at least one paper sheet within said sheet feeding channel to be fed forwardly in a first direction; a sheet stopping structure for stopping said at least one paper sheet from being moved in said first direction; plural sensing arms disposed between said sheet feeding structure and said sheet stopping structure and arranged along a second direction, which is perpendicular to said first direction, wherein each of said sensing arms comprises a contacting terminal, a sheltering terminal and a rotary part, wherein said rotary part is arranged between said contacting terminal and said sheltering terminal, wherein when said at least one paper sheet is contacted with said contacting terminal, said sensing arm is rotated by using a center axel of said rotary part as a pivot; at least one optical sensor comprising a light transmitter and a light receiver, wherein when a light beam from said light transmitter is received by said light receiver, said optical sensor issues a first signal, wherein when said light beam from said light transmitter is sheltered by said sheltering terminal of any sensing arm, said light beam fails to be received by said light receiver, and said optical sensor issues a second signal; and wherein when said light beam from said light transmitter is again received by said light receiver said optical sensor issues a third signal; a controller connected with said optical sensor and said sheet stopping structure, wherein if said first signal, said second signal and said third signal are sequentially received by said controller, said sheet stopping structure is controlled by the controller to allow said at least one paper sheet to be continuously moved forwardly in said first direction.
 2. The sheet feeding apparatus according to claim 1 further comprising a feed sensing module for detecting whether said at least one paper is placed in said sheet feeding channel, wherein said controller is connected with said sheet feeding structure and said feed sensing module, wherein when said feed sensing module detects that said at least one paper is placed in said sheet feeding channel, said feed sensing module issues a third signal to said controller, wherein in response to said third signal, said sheet feeding structure is enabled by said controller.
 3. The sheet feeding apparatus according to claim 2 wherein said feed sensing module comprises: a second optical sensor comprising a second light transmitter for emitting a second light beam and a second light receiver for receiving said second light beam; and a feed sensing structure comprising a sheet feeding part, a sensing part and a rotary shaft, wherein said sheet feeding part and said sensing part are fixedly connected with said rotary shaft, and said sensing part is arranged between said second light transmitter and said light receiver, wherein when said at least one paper sheet is not contacted with said sheet feeding part, said second light beam from said second light transmitter is sheltered by said sensing part, so that said second light beam from said second light transmitter fails to be received by said second light receiver, wherein when said at least one paper sheet is contacted with said sheet feeding part to push said sheet feeding part, said sheet feeding part is rotated by using said rotary shaft as a pivot and said sensing part is rotated with said sheet feeding part, so that said second light beam from said second light transmitter is received by said second light receiver.
 4. The sheet feeding apparatus according to claim 2 wherein said feed sensing module comprises: a second optical sensor comprising a second light transmitter for emitting a second light beam and a second light receiver for receiving said second light beam; and a feed sensing structure comprising a sheet feeding part, a sensing part and a rotary shaft, wherein said sheet feeding part and said sensing part are fixedly connected with said rotary shaft, wherein when said at least one paper sheet is not contacted with said sheet feeding part, said second light beam from said second light transmitter is received by said second light receiver, wherein when said at least one paper sheet is contacted with said sheet feeding part to push said sheet feeding part, said sheet feeding part is rotated by using said rotary shaft as a pivot and said sensing part is rotated with said sheet feeding part, so that said second light beam from said second light transmitter is sheltered by said sensing part and fails to be received by said second light transmitter.
 5. The sheet feeding apparatus according to claim 1 wherein said sheet feeding structure comprises a feed roller and a feed roller shaft, wherein said feed roller is fixedly connected with said feed roller shaft, and said feed roller is rotated as said feed roller shaft is rotated.
 6. The sheet feeding apparatus according to claim 5 wherein said sheet stopping structure comprises plural sheet stopping arms and a sheet stopping shaft, wherein said sheet stopping shaft is parallel with said feed roller shaft, and said plural sheet stopping arms are disposed on said sheet stopping shaft and arranged along said second direction.
 7. The sheet feeding apparatus according to claim 1 further comprising a fixing shaft, wherein both ends of said fixing shaft are respectively fixed on two sides of said sheet feeding apparatus, and said rotary part of each sensing arm is pivotally coupled with said fixing shaft.
 8. The sheet feeding apparatus according to claim 7 wherein said rotary part of each sensing arm is a cylindrical post. 